Contact-telephone



(No Model.) T. A. WATSON.

Contact Telephone[ No. 242,721. Patented June 7,1881.

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iUNITED STATES PATENT OFFICE.

THOMAS A. WATSON, OF EVERETT, MASSACHUSETTS.

CONTACT-TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 2e2,721, dated June '7,1881.

Application filed April 7, 1831. (No model.)

T 0 all whom it may concern:

Be it known that I, THOMAS A. WA'rsoN, a citizen of the United States,of Everett, in the county of Middlesex and State of Massachusetts, haveinvented certain Improvements in Contact or Microphonic Telephones, ofwhich the following is a specification.

My invention relates to that class of instruments known as microphonicor contact telephones, in which the impact of the soundwaves on thetransmitting-diaphragms and the vibrations resulting therefrom so'actupon a variable resistance included in the circuits as to cause the saidresistance alternately to increase and diminish. The continuous currentof a galvanic battery flowing in the ciror less rigidly attached to thediaphragm, and

a second electrode normallymaintained in contact with the first by acertain initial pressure and suspended on asprin gor pendulum. Otherforms of batterytelephones have been constructed in .which bothelectrode and phragm are rigidly supported.

when instruments of the firstmen'tioned class are used the spring orpendent electrode, not being entirely under control of the soundwaves,will introduce extraneous vibrations, which, not belonging to the soundsintended to be transmitted, consequently tend to confuse and render themindistinct.

It has also been ascertained by experience that battery-telephones ofthe second class which I have cited, by reason of the rigidity of thediaphragm and electrodes, have such a limited range of adjustment thatin practice they cannot be used with a great degree of success for anyprotracted period of time. When such transmitters are, however, broughtto their proper adjustment they give much bett-er results than thoseprovided with a rigid diaphragm and spring or pendulous electrodes.

The objects, then,of myimprovement are to combine the good qualities ofbotlrforms of transmitter, and while maintaining a "wide rangeQfadjustment to improve the strength and steadiness of thetransmittedtones, and,

generally, to increase the efficiencyot' the apparatus.

To this end my invention consists, first, in the use of a diaphragmsuspended upon springs at a distance from the front of its casingsecond, in the combination of a diaphragm or resonant plate suspended onsprings having a conducting-electrode firmly attached thereto, and bythe elasticity of the diaphragm-supporting springs normally maintainedin contact with a second electrode mounted on a rigid support, and amouth-piece or tubepassing through and supported by the front of theeasing, and so arranged as to direct the entire force of the sound-waveson the center of the diaphragm.

In the accompanying drawings, Figure 1 is a sectional view of myimproved contact-telephone. Fig. 2 is a sectional view on the line as aof Fig. 1, looking at the diaphragm; and Fig. 3 is a diagrammaticrepresentation of a telephonic circuit, showing my apparatus used at onestation as a transmitting and at the other as a receiving telephone.

In the figures, Ais the casing or box inclosin g the operating parts.

suitable material. This is pierced through the B is the front of saidcasing, and may be made of wood or any other It has been ascertained byexperience that center for the reception of the mouth-piece O, i

which is firmly fixed therein. The end of the mouth-piece, passingcompletely through the block B a suitable distance, is brought intoclose proximity to, but not allowed to touch, the diaphragm D nearitscenter. The diaphragm D is supported by three steel springs, E E E, eachof which is by one end riveted to it at equal distances one from theother, while the other end of each spring is brought round and fastenedby a screw to the wooden blockor front supporting-board, B. Thediaphragm is thus hung by the three springs at a distance from the frontboard, and a rubber ring is placed round its edge, as usual.

To the center of the diaphragm D is rigidly attached, by a screw throughthe plate, a carbon button, I), which forms a part of the electriccircuit, and is pressed by the vibrations of the diaphragm with avarying degree of force against the opposing electrode or complementarycontact-point c. This contact-point 0 also is a button or stud of carbonarranged in a setting of brass on the end of an adjustingscrew, d, whichmay by its milled head 0 be screwed up so as to impart to the contact ofthe electrodes b and c any required degree of initial pressure.

The wires to 'w of the circuit leading to and from the battery areattached one to the screw a of the diaphragm-spring E and the other toany part of the frame or case A which is in metallic connection with theadjusting-screw d or electrode 0. The whole casing, with the exceptionof the front covering, B, may, if desirable, be made of metal.

The position of the springs E E E with reference to each other isclearly shown in Fig. 2.

In Fig. 3, 1 represents a telephone-station at one end of a line, to,while 2 is a station at the other end. P is a battery included in thecircuit, and the entire circuit terminates at both ends in the earth.This I have shown to illustrate the adaptability of my invention for useas areceiving-telephone in addition to its ordinary use as atransmitter. Its pencil-electrodebeing rigid, and the diaphragm D, owingto the elasticity of its supporting-sprin gs, being free'to. vibrate asa whole in a manner resemblin g the motions of the piston of asteamengine, repulsion between the contacts I) and 0 will be necessarilyexpended on the diaphragm, whereas in the ordinary forms of spring orpendulous electrode instruments it would be expended in moving theelectrode, without materially affecting the diaphragm. Therefore myinvention is eminently adapted for use as a contact-receiving telephone,on the principle enunciated by Emile Berliner in his patent of November2, 1880, No. 233,969.

The method of arranging the mouth-piece O by bringing it near to thediaphragm in an open air-space instead of a close air-chamber isadvantageous, as, while the sound-waves are concentrated on the centerof the diaphragm, undue condensation of the air and the hollow soundsresulting therefrom are prevented.

My improved instrument is ordinarily to be used in connection with thewell-known appurtenances of a local battery and induction-coil, whichare employed in the practical application of this class of instruments;but these instrumentalities form no part of my invention,

and consequently are not herein shown, described, orclaimed. Neither doI claim herein a diaphragm or vibrating plate freely suspended by aspring, hinge, or pivot, as that I have made the subject-matter of aseparate application.

Although in this embodimentof my invention I have described thediaphragm as being mounted on three springs of the conformation shown inthe drawings, I do not confine myself to this precise shape or number,but may, without departingfrom the spirit of my invention, modify eithershape or number, or both, or in place of the springs substitute anymechanical equivalent therefor.

Having now described my invention, what I claim is 1. In acontact-telephone, the combination of a diaphragm or vibratory platesuspended to produce, under the influence of sound-waves,

free rectilinear vibrations, and a rigid contactpoint, substantially asdescribed.

2. In a contact-telephone, a diaphragm or vibrating surface which,instead of being rigidly clamped to the frame, is mounted on springs ata distance from the front piece or frame, and adapted by the elasticityof said springs to vibrate freely under theintluence of sound-waves,thereby varying its pressure on a rigid or immovable electrode orcontact-point, substantially as described.

3. The combination, in a contact-telephone, of a spring-supporteddiaphragm carrying one contact-electrode of an electric circuit, and therigidly-mounted opposite or complementary contact-electrode.

4. The combination, in a microphonic telephone, of a diaphragm supportedon springs at a suitable distance from the frame of the instrument andcarrying one electrode, a rigid or immovable opposite electrode, and amouthpiece extending through the front of the casin g and adjusted inclose proximity to the diaphragm, substantially as and for the purposdescribed.

5. The combination,with a spring-supported THOMAS A. WATSON. Witnesses:

Tnos. D. LocKWoon, W. G. ToMPKINs.

